This application is based on application No. 10-68988/1998 filed in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an image processor which receives color image data and converts them to image data used for image forming.
2. Description of Prior Art
In reproduction of a color image, it is known generally to detect character edges in input color image data and to emphasize the edges according to the detection results. This improves reproducibility of characters by emphasizing gradation contrast of the background and the characters. However, whitening arises due to contrast emphasis around the characters, and the characters are bordered. Then, in a proposed method, boundaries are detected between characters and the background, and peripheral portions of the characters are detected. Then, the lowest density level among the peripheral pixels is selected in the peripheral portions of the characters.
The proposed method can solve the problem of partial whitening in the peripheral portions of the characters, but there is a problem of bordering of the characters. As to bordering due to edge emphasis at the characters, the obtained image is not so disagreeable if the line width of the character image is wide. However, as to a particular line width, an area disposed between two character edge areas becomes as narrow as one or two dots, and partial disappearance of characters may happen. This phenomenon deteriorates character reproducibility although edge emphasis is performed.
An object of the present invention is to provide an image processor which improves reproducibility of character edges.
In one aspect of the invention, in an image processor which processes image data of an image consisting of a plurality of pixels, a first allocator decides an edge portion in the image included in the image data and allocates a specified attribute as an attribute of pixels located in the edge portion. Then, a second allocator allocates the specified attribute as an attribute of pixels located in an area interposed between two edge portions.
In another aspect of the invention, in an image processor which processes image data of an image consisting of a plurality of pixels, a first allocator decides a boundary portion between a character image and a background in the image included in the image data and allocates a specified attribute as an attribute of pixels located in the boundary portion. Then, a second allocator allocates the specified attribute as an attribute of pixels located in an area interposed between two boundary portions. An area discriminator discriminates whether each of the image data belongs to a character image area or a background image area, and a corrector performs a specified correction for image data of the pixels to which the specified attribute is allocated by the first and second allocators according to discrimination by the area discriminator.
An advantage of the present invention is that partial whitening in characters is prevented when they are reproduced and that the reproducibility of characters is improved by discriminating character edges.